Convert enable_plugins to a buildflag header.

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index 581fdf2e28fd6d90c20d3d32884843e365e90f62..6d8a898fdc971bf7be056cb377e93bb0c9e7c5c2 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -7,6 +7,7 @@
 #include "base/base_switches.h"
 #include "base/command_line.h"
 #include "build/build_config.h"
+#include "ppapi/features/features.h"
 #include "printing/features/features.h"
 
 namespace switches {
@@ -1244,7 +1245,7 @@ const char kWindows8Search[]                = "windows8-search";
 const char kDebugPrint[] = "debug-print";
 #endif
 
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
 // Specifies comma-separated list of extension ids or hosts to grant
 // access to CRX file system APIs.
 const char kAllowNaClCrxFsAPI[]             = "allow-nacl-crxfs-api";